1. Technical Field
The present invention relates to techniques for simplifying the structure of electro-optical devices such as liquid crystal display devices.
2. Related Art
In an electro-optical device for performing display using electro-optical changes, such as a liquid crystal device, pixels are provided at intersections of scanning lines (gate lines) and data lines (source lines). Each of the pixels generally includes a capacitor holding an electro-optical material, such as liquid crystal, between a pixel electrode and a common electrode having a constant potential, and a switching element that establishes conduction between the data line and the pixel electrode when the scanning line is selected. The grayscale level (or brightness) of each pixel is determined by an effective voltage value stored in the capacitor. In a case where liquid crystal is used as the electro-optical material, the pixels are basically alternating-current driven, and a data signal designates a voltage for a range of grayscale values from the highest grayscale value to the lowest grayscale value on the high-level (or positive-polarity) side with respect to a reference potential, and a voltage for a range of grayscale values from the highest grayscale value to the lowest grayscale value on the low-level (or negative-polarity) side with respect to the reference potential.
A technique in which high and low voltages are alternately applied at certain intervals, such as every horizontal scanning period, to a common electrode to narrow the voltage range of a data signal, thereby achieving simplification of a circuit for driving data lines has been proposed (see, for example, JP-A-62-49399).
Although the technique allows simplification of a circuit for driving data lines, there arises another problem in that a wider voltage range may be required for switching elements of pixels and a scanning line circuit for driving scanning lines.